1. Field of the Invention
The invention relates to a method for manufacturing an optical device, and more specifically to a method for manufacturing an optical filter.
2. Description of the Related Art
The color filter is a key element in the colorization of liquid crystal displays (LCD) because LCD displays with high gray scale output display full-color using a color filter. More specifically, the color filter generates the three primary colors of red (R), green (G) and blue (B) by way of filtering. The three primary colors are mixed by the color filter according to various proportions of each of the primary colors so as to represent various colors. Accordingly, the LCD may then display full color.
In general, the color filter includes multiple R, G, and B pixel formations on a glass substrate. Therefore, after passing through these pixels, the white backlight becomes R, G, and B light rays, which constitute the three primary colors. Methods often used for manufacturing conventional color filters include a printing method, dyeing method, pigment dispersion method, dry-film method, an electrode position method, and the like, wherein the pigment dispersion method is the primary method available in the market. A conventional method for manufacturing a color filter will be described using the pigment dispersion method as an example.
Referring to FIG. 1, the conventional method for manufacturing a color filter includes the following steps.
First, in the conventional method for color filter manufacturing, a glass substrate 11 is provided, and the glass substrate is cleaned with a cleaner (not shown). For example, the glass substrate 11 often used to manufacture a thin film transistor (TFT) is the non-alkali type glass, while the method often used for cleaning is the ultra-violet (UV) cleaning method. The UV cleaning method utilizes UV rays to convert oxygen molecules in the air into ozone molecules, which dissolve the remaining organic substances on the glass substrate 11. The UV cleaning method can clean organic substances with a maximum thickness of about 100 angstroms. The UV cleaning method mentioned above may also be referred to as the dry cleaning method. Other methods, in which a cleaning agent or deionized water is added, may be referred to as wet cleaning methods.
The clean glass substrate 11 is coated with a photo-resist (PR) 12 of the required color, such as a red photo-resist. The materials constituting the photo-resist 12 may include resin, photo-active compounds (PAC), and solvents. Photo-resists suitable for the photo-resist 12 may be divided into a positive photo-resist and a negative photo-resist according to its property against light rays. The positive photo-resist may be dissolved in a developer and is typically used in the manufacturing processes of high-resolution products (e.g. TFT-Arrays). Alternately, the negative photo-resist does not dissolve in a developer and is typically used in manufacturing processes greater than 3 μm, such as the manufacturing processes for color filters. In addition, the photo-resist 12 is coated on the glass substrate 11 in the coating process. In the coating process, a tube may be used to lower the photo-resist 12 from the center of the glass substrate 11, or a slit may be used to coat a layer of photo-resist 12 on the glass substrate 11. After the photo-resist 12 is coated, the glass substrate 11 is spun and causes the photo-resist 12 to uniformly coat the glass substrate 11.
Next, a photolithography process is performed to form a pattern, as designed on the mask 60, on the photo-resist 12. In detail, the glass substrate 11 coated with the photo-resist 12 is transferred to an exposure machine (not shown). Then, the procedures of pre-alignment, proximity gap measurement, mask pattern alignment, exposure, and the like are performed in the exposure machine. By performing the procedures, a desired pattern may be formed on the photo-resist 12.
The mentioned color filter is further coated with a plurality of photo-resists having various colors, such as a green photo-resist 13 and a blue photo-resist 14. It should be noted that the steps for forming the photo-resists 13 and 14 are performed by repeating the above-mentioned coating, photolithography, and development processes.
Finally, a post-baking process is performed to fully cure the photo-resists 12 to 14 so as to prevent the photo-resists 12 to 14 from being easily stripped in the following processes.
In addition, for some specific products, an over coat layer 15 must be formed on photo-resists 12 to 14 so that the surface of the color filter can be made smoother and the photo-resists 12 to 14 can be protected.
However, since the conventional method for manufacturing the color filter utilizes the mask 60 in the photolithography process, the mask 60 must be formed according to a desired pattern. Furthermore, an exposure machine must be used to perform the procedures of alignment, exposure, and the like. The mask and the exposure machine may present additional costs to the manufacturer.
Consequently, it is an important subject of the invention to provide a method for manufacturing an optical device without using a mask to perform a photolithography process.